As is known in the art, High Electron Mobility Transistors (HEMTs) based on group III nitrides require low buffer and low gate current leakages to minimize losses. GaN HEMTs grown by Molecular Beam Epitaxy (MBE) have traditionally shown good “on”-state performance, but high leakage in the “off”-state.
As is also known in the art, doped semiconductors are semiconductors which contain impurities, foreign atoms which are incorporated into the crystal structure of the semiconductor. These impurities can either be unintentional due to lack of control during the growth of the semiconductor or they can be added on purpose to provide free carriers in the semiconductor. For example, in growing layers of a HEMT using MBE, contaminants in the MBE equipment introduce background material or so-called UnIntentially Doped (UID) regions in the MBE grown layer. These UID regions typically have doping concentrations of 5×1014 to 5×1016 atoms per cm3 or less. Thus, as used herein, an UID region or layer is considered as comprising material or particles that are unintentional due to lack of control during the growth of the semiconductor and/or have doping concentration typically of 5×1014 to 5×1016 atoms per cm3 or less.